Matilda went to one nap a day at 13 months when we were at a sleep school. At that time I told the nurses that was what I thought was happening & they kept saying it was heaps young to go to one nap a day. But in the end, Matilda won . I say like Lucy, go with the signs and watch him. If he needs it, he will keep sleeping. Otherwise, Matilda went from having a normal nap in the morning to not sleeping during her afternoon naps at all... and thats when we tried to keep her up in the morning & let her only have one nap. She did much better for it.